Mobile concrete batch plant and dual shiftable mobile mixers therefor

ABSTRACT

A mobile concrete batch plant supplies batches of cement and aggregate (and water) from its elevated discharge end alternately to the tiltable rotary drums of a pair of self-erecting mobile mixers which are arranged side-by-side and laterally shiftable on guide rails disposed transverse to the longitudinal axis of the plant beneath the discharge end of the plant. Means are provided for shifting the mixers back and forth simultaneously on the guide rails so that the drum of one mixer is being loaded while the drum of the other mixer is discharging into a mix truck or dump truck therebeneath.

United States Patent Alhin l l June 10, 1975 l l MOBILE CONCRETE BATCH PLANT AND 2.351202 6/[944 111111150" l. 259/l6l DUAL SHIFTABLE MOBILE NHXERS 1984,46! 5/l96l Butler 61 al 1 1 l 1 1 l 1 259/57 3.3l7,l94 5/l967 Heltzel 259/161 THEREFOR 3.fil7 ll3l ll/l97l Paris 259/l77 R [75l Inventor: Max D. Albin, Urhana. Ill. [7H Assignee: Koehring Company. Milwaukee. 'i Exami',ler Harvey Hlomsby w Assistant Examrm'r lames A. Nlegowskl Attorney, Agent, o Firm-Andrew 1. Beck 22 Filed: Feb. 26, 1974 [21 I Appl, No.: 446,004 ABSTRACT A mobile concrete batch plant supplies batches of ce- [52] Us Cl u 259/17]: 259/57 259/177 A ment and aggregate (and water) from its elevated dis- [51 I 1'. CH H 828C 7/14: 828C 9/04 charge end alternately to the tiltable rotary drums of a [58] Field of Search U 259/161 6 163 pair of self-erecting mobile mixers which are arranged (J/m5 169 I70 side-by-side and laterally shiftable on guide rails disl77 Q C posed transverse to the longitudinal axis of the plant R &- H [7 R R beneath the discharge end of the plant. Means are Ian/242; 5 252 5 provided for shifting the mixers back and forth simultaneously on the guide rails so that the drum of one {56} References Cited mixer is being loaded while the drum of the other mixer is discharging into a mix truck or dump truck UNITED STATES PATENTS thgrebeneath' 2,073,652 3 1937 Rohb .1 259 152 2,264,039 11/1941 Hoya v, 259/l6l 10 Chums, 7 Drawmg Flgllres PATENTEDJUH I 0 1915 Sl-iEET SHEET PATENTEUJUH 10 I915 PATENTEUJUN 10 I975 CONTROL F'IG.6

MOBILE CONCRETE BATCH PLANT AND DUAL SHIFTABLE MOBILE MIXERS THEREFOR BACKGROUND OF THE INVENTION 1. Field of Use This invention relates generally to mobile concrete batch plants and to mobile self-erecting mixers having rotatable tiltable drums supplied from the batch plants and adapted to discharge into vehicles such as dump trucks or mix trucks.

2. Description of the Prior Art The prior art discloses various arrangements wherein concrete batch plants supply batches of cement and aggregate (and necessary water) to a plurality of tiltable rotary mixer drums in such a manner that one mixer drum is being loaded while another previously loaded completes its cycle of mixing and unloading. For exam ple, US Pat. No. 2,352,202 issued June 27, 1944 to C. H. Johnson for Mixing Plant" teaches an arrangement wherein a concrete batch plant employs a plurality of alternately usable chutes to supply batches of mix to a series of tiltable rotary mixer drums which are stationarily mounted in a circle about a centrally located receiving hopper into which they each discharge. I-loya US Pat. No. 2,264,039 and Robb US Pat. No. 2,073,652 show generally similar arrangements. It is also known to provide a plurality of mobile self-erecting tiltable rotary mixer drums which are alternately supplied from a mobile concrete batch plant by means of a conveyor on the batch plant which can be swung to various positions to supply each mixer drum as required.

SUMMARY OF THE PRESENT INVENTION In accordance with the present invention there is provided a mobile (towable) concrete batch plant for supplying weighed batches of cement and aggregate (and necessary water) from a raised discharge end thereof to the rotary tiltable drums of a pair of mobile (towable) self-erecting mixers which are temporarily joined together in side-by-side relationship and mounted on guide rail means disposed adjacent the discharge end of the batch plant and transverse to the longitudinal centerline of the batch plant. Means are provided for rotating each mixer drum and for tilting each mixer drum between load (charge) and unload (discharge) positions. Means are also provided for moving both mixers back and forth on the guide rail means so that one upwardly tilted mixer drum is in a location to be charged from the batch plant while the other mixer drum is in another location offset from the longitudinal centerline of the batch plant wherein it can be downwardly tilted and discharged.

In the embodiment of the invention disclosed herein, the batch plant comprises a supporting frame having conventional ground wheels at its rear end, a tow hitch at its front end, and detachable supports or legs for supporting its front end in raised position. Mounted on the frame are an aggregate storage bin which discharges aggregate into an aggregate weigh batcher, a belt'type aggregate conveyor for transporting a weighed batch of aggregate from the aggregate weigh bin to a raised discharge chutc which supplies the mixers, and a cement storage bin which discharges cement into a screwtype cement conveyor for transport to a cement weigh batcher which discharges a weighed batch of cement into the aforesaid discharge chute.

Furthermore, each mixer comprises a main frame (having conventional ground wheels at its rear end and a tow hitch at its front end a platform mounted on the main frame and selectively movable vertically by hydraulic rams between lowered and raised positions. a drum support yoke mounted on the platform and selectively tiltable by hydraulic rams between upright and downwardly tilted positions, and a drum having an opening for receiving and discharging batches of material, said drum being mounted for rotation on the yoke by means of selectively operable hydraulic motors. The main frame of each mixer is also provided with railengaging wheels for supporting the mixer for lateral movement on the guide rail means, each rail-engaging wheel having its axis of rotation transverse to the axis of rotation of the mixer drum and wheels. Means are also provided to detachably connect the main frames of a pair of mixers together in side-by-side relationship.

Furthermore, the guide rail means comprise a pair of parallel spaced apart guide rail assemblies which are detachably mounted on a rigid demountable ground engaging foundation pad and each guide rail assembly comprises a lower mixer support rail and an upper rail which prevents the mixers from tipping over if unbalanced.

THE DRAWINGS FIG. 1 is a perspective view of a mobile concrete batch plant and two mobile self-erecting mixers having tiltable rotary drums, said mixers being arranged sideby-side and mounted for lateral shifting movement on guide rails beneath the raised discharge end of the plant",

FIG. 2 is a side elevation view of the batch plant of FIG. I in over-the-road travel position;

Flg. 3 is a side elevation view of a mixer of FIG. I in over-the-road travel position;

FIG. 4 is a side elevation view of the arrangement shown in FIG. 1;

FIG. 5 is a top plan view of the arrangement shown in FIGS. 1 and 4;

FIG. 6 is an elementary, schematic diagram of the electrohydraulic control system for the mixers shown in FIGS. 1, 3, 4 and 5; and

FIG. 7 is an enlarged perspective view showing details of a foundation pad and guide rail means shown in FIG. 4.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. I is a perspective view showing a mobile concrete batch plant 10 in its raised on-site working position and a pair of mobile self-erecting rotary tiltable cement mixers II and 12 connected together in side-byside relationship for shifting movement on guide rail means, comprising guide rail assemblies 13 and 14 and a foundation pad 15, in a direction transverse to the longitudinal axis of plant 10. Plant 10 supplies weighed batches of cement and aggregate (including sand, if desired) and any necessary water first to one mixer and then to the other. While one mixer is in one location aligned with the longitudinal axis of the plant I0 wherein it is being loaded or charged from plant 10, the other mixer is in another location laterally offset from the longitudinal axis of the plant in another location wherein it completes its mixing cycle and can be un- 3 loaded or discharged into a mix truck or dump truck 20.

As FIGS. 1, 2 and 4 show, batch plant generally comprises a rigid support framework 21, formed of structural steel members. having rearwardly disposed conventional ground wheels 22 and a forwardly disposed tow hitch 23 adapted for connection to a tow truck (not shown). Plant 10 assumes the position shown in FIG. 2 for over-the-road transport or towing and assumes the position shown in FIGS. 1 and 4 when installed in on-site working position wherein its dis charge end is raised and supported by means of detachable forward and intermediate support braces or legs 24 and 25, respectively. Framework 21 is provided with a rearwardly located ground engaging brace 26 which enables its wheels 22 to rise clear of the ground when plant 10 is raised.

Plant 10 further comprises the following components which are mounted on or supported by framework 21, namely: a multi-compartment aggregate storage bin 30 having a plurality of remotely and independently operable discharge gates or doors A, 15B and 15C; an ag gregate weigh bin or weigh batcher 31 for receiving aggregate from aggregate storage bin and having a single remotely operable discharge gate or door 32; a flexible belt-type aggregate conveyor 33 driven by an electric motor 35 for receiving a weighed batch of aggregate from aggregate weigh batcher 31 and for delivering it to the raised discharge end of the plant for charg ing the mixers 1] and 12; a cement storage bin having a remotely operable discharge gate or valve 41', a screwtype cement conveyor 42 driven by an electric motor 43 for receiving cement from cement storage bin 40 and for delivering it to a cement weigh bin or weigh batcher 45 having a single remotely operable discharge gate or door 46 for delivering a weighed batch of ce ment to a swingable chute 47 for charging the mixers 11 and 12.

The aggregate weigh batcher 31 and the cement weigh batcher 45 are suspended or supported on framework 21 in a conventional manner by means of conventional scale levers 50 and 51, respectively. which are connected by conventional pull-rods 52 and 53, respectively, to conventional prcsettable dial type scales 54 and 55, respectively, which provide a visual readout of batch weights and are presettable to provide electric control signals to a control panel on plant 10 for use in operation of the plant in automatic, semiautomatic or manual modes. Control panel 60 is understood to comprise manually operable control switches and electrical circuitry which enable operation of plant 10 in its various modes.

It is to be further understood that the several gates, valves and doors hereinbefore referred to could be operated automatically by electrical, hydraulic or pneumatic actuators of a conventional type.

Plant 10 also comprises an air compressor 61 for for supplying compressed air used for cement aeration (through a pipe 62) and any pneumatic components required. and also comprises a water pipe 63. a water meter 64 and a water control valve 65.

The mixers 11 and 12. shown in FIGS. 1, 3. 4, 5, and 6. which are alternately supplied from plant 10 with weighed batches of cement and aggregate and necessary water are substantially identical to each other and, therefore. only mixer 11 is hereinafter described in detail. FIG. 3 is a side view showing mixer 11 disposed in condition for over-the-road transport by means of a tow truck, for example. and FIGS. 1 and 4 show mixers 11 disposed in its fully-erected "-o ing condition wherein it can conveniently be charged from plant 10 and discharged into truck 20 passing beneath a portion thereof. Mixer 11 comprises a rig I i mework 70, formed of longitudinal and transverse structural steel members 71 and 72, respectively, having rearwardly disposed conventional ground wh.:els 73 and a forwardly disposed tow hitch 74 adapted for connection to a tow truck (not shown]. A protective shield 75 is rigidly mounted at the rearward end of framework 70. Mixer 11 also comprises a rigid platform 76 which can be moved between a fully-lowered position (shown in FIG. 3) and a full raised position (shown in FIGS. 1 and 4) by means ofa pair of retractable and extendable hydraulic rams 77 and 78. Each of the rams 77 and 78 is pivotally connected at its lower end as by a pin 79 to main framework 70 and at its upper end as by a pin 80 to platform 76. A pair of forward support braces 82 and a pair of rearward support braces 84 for platform 76 are also pivotally interconnected between framework 70 and platform 76. More specifically, each support brace 82 and 84 is pivotally connected to framework 70 as by a pin 85 and to platform 76 as by a pin 86.

Platform 76 is provided on the opposite sides thereof with a spaced apart rigid support structures 89 and 90 on which a generally U-shaped drum support yoke 91 is pivotally mounted as by pins or trunnion mounts 92. Yoke 91 is tiltable between a drum charging position (shown in FIG. 4 by solid lines) and a drum discharging position (shown in FIG. 4 by broken lines) by means of a pair of hydraulic tilt cylinders or rams 95, each of which rams is pivotally connected to platform 76 as at 96 and to yoke 91 as at 98.

Mixer 11 further comprises a hollow drum 100 which, for example, is mounted for rotation on yoke 91 as by means of large support rollers 101 carried on the inside of the legs of yoke 91. Drum 100 is driven by a pair of electric motors 103 and 104 which are sup ported on and movable with yoke 91. c drive shaft 106 of each motor 103 and 104 is provided with a drive gear 107 which is in constant mesh with it large toothed drive ring 108 which is rigidly secured to the base end of drum 100. Drum 100 is provided with a mouth or opening 110 through which it is charged and discharged.

As FIGS. 4, 5 and 6 show, main framework 70 of mixer 11 is provided with four rail-engaging wheels 112, 113, 114 and which are generally disposed near the four corners of the framework to provide balanced support for the mixer on the guide rail assemblies 13 and 14. Each wheel 112 through 115 is pro vided with an axle about which it rotates and by means of which the wheel is supported for rotation on framework 70. As FIGS. 5 and 6 show, the wheels 112 through 115 (and, thus, their axes of rotation) are transverse (ie, at right angles) to the ground engaging wheels 73 and drum 100. FIG. 6 shows that railengaging wheel 1 12 is connected to and driven by a hydraulic motor 122, but other wheels 113, 114 and 115 could also be driven if desired. As is apparent from FIG. 3, the wheels 112 through 115 are mounted so as to be disposed well above ground or road level when the mixer 11 is being towed or at rest. Also, as FIG. 4 shows, the ground wheels 73 are disposed above ground level and clear of the guide rail means and foundation pad components when the mixers 11 and 12 are mounted thereon.

Each mixer ll and 12 can be placed or mounted on the guide rail means in several possible ways but a preferred way is to assemble the foundation pad 15 and place the lower guide rails thereon and to then employ a heavy duty fork lift type unit or crane to lift the mixers (while still unerected) and place them upon the lower rails. after which the upper guide rails and their supports are assembled and the two mixers are joined together and erected. Disassembly procedures would be the reverse of those described.

As FIGS. 4 and 5 show. the foundation pad 15 on which the guide rail assemblies 13 and 14 are mounted is rectangular in configuration and comprises four rigid structural steel member, such as l-beams 130. 131, 132 and 133, which are releasably connected together at their corners by suitable bolts 134. The members forming pad 15, when disassembled. may be conveniently transported to and from a job-site on plant or on a separate vehicle. Pad is mounted on a flat level portion of earth which has been prepared or graded for this purpose. as by a bulldozer or scraper. As FIG. 4 shows. it may be necessary in some instances. depending on the height of the plant 10 and mixers 11 and 12 when disposed in working condition. to dispose the mixers at a lower grade level than that of the plant.

As FIG. 7 shows in detail. each guide rail assembly 13 and 14 comprises a lower guide rail 137 similar in configuration to a length of railroad track releasably connected and rigidly supported on pad 15 as by bolts 138. Each guide rail assembly 13 and 14 also comprises an upper guide rail 139. similar to rail 137. releasably connected and rigidly supported in inverted condition on two or more support mounts such as 140 as by bolts 141. The rails 137 and 139 and the mounts 140 are also transportable to and from the job site in the same manner as the members of pad 15. The lower rails 137 support the full weight of the mixers ll and 12 and their loads and the upper rails 137 prevent the mixers from tipping over if they reach an unbalanced condition, as during dumping.

As FIG. 5 shows. means are provided to secure the mixers 11 and 12 together in side-by-side relationship for simultaneous movement back and forth on the guide rail means and. in its simplest form such means comprise a series of releasable bolts 144 (and associ ated nuts) which extend through and secure together the adjacent longitudinal members 71 and 72 of the mixers 11 and 12, respectively. If necessary, appropriate spaces such as 145 could be provided to ensure nec essary clearance between the adjacent mixers. However. other types of means for releasably securing the mixers 11 and 12 together could be employed.

FlG. 6 shows an elementary schematic diagram of an electrohydraulic control system for operating and moving the mixers 11 and 12. In FIG. 6 an electric motor 150 operated by means of an electrical control panel 151 mounted on mixer ll drives a hydraulic pump 152 which supplies hydraulic fluid from a reservoir 153 to solenoid operated hydraulic fluid flow control valves. hereinafter described. which. in turn. direct fluid to the hydraulic motors and rams. as hereinafter described. Electrical control panel 151 also operates the electric motors 103 and 104 on the mixers 11 and 12.

More specifically. pressure port P of pump [52 supplies pressurized fluid through hydraulic supply lines 155. 156,157,158. 159 and 160 to the input ports W of the three'positionmeutral or off; forward or up; reverse or down) variable or proportional flow. solenoid operated hydraulic control valves 161. 162, 163, 164. l and 166, respectively. The fluid return ports OP of the last-mentioned valves are connected by fluid return lines to fluid reservoir 153. The last-mentioned valves are to be understood to be. for example, conventional types of valves wherein the volume of fluid flow therethrough is proportional to the extent of movement of the valve spindle so that the operating speed of the hydraulic rams or motor can be controlled. Valve spin dle movement on the other hand is proportional to the current flow (or applied voltage) in the valve solenoid.

The erection control valves 161 and 164 are con nected to and control operation of the erection rams 77 and 78 of the mixers 12 and 11, respectively. The drum tilt control valves 165 and 166 are connected to and control operation of the respective drum tilt cylinders of the mixers l1 and 12. respectively. The traverse control valves 162 and 163 are connected to and con trol operation of the traverse drive motors 122 for the mixers l2 and 11, respectively. As FIG. 6 shows. the solenoid coils of the several valves are connected by suitable electrical control wires. generally designated CW, to control panel 151. The motors 103 and 104 are similarly connected to panel 151 by suitable electrical control wires MW.

OPERATION Assume that plant 10, the foundation pad 15, the guide rail assemblies 13 and 14, the mixers ll and 12 and their drums are initially arranged and disposed on ajob site in the condition shown in FlGS. 1. 4. S and 6 and that the bins 30 and 40 of plant 10 are filled and the elevated upwardly tilted drums 100 are empty.

Plant 10 is then operated so that the gates 15A. 15B. 15C open to supply a predetermined amount of aggregate from aggregate bin 30 to aggregate weigh bin 3] whereupon those gates close. Subsequently, gate 32 opens to discharge aggregate from aggregate weigh bin 31 onto belt conveyor 33 which is already in operation and transports the aggregate to chute 47 from whence it is discharged into drum 100 of mixer 11 which is in axial alignment with the longitudinal centerline of plant 10. Gate 41 also opens to supply cement from cement storage bin 40 to the lower end of screw conveyor 42 which operates to deliver a predetermined amount of cement to cement weigh bin 45, whereupon gate 41 closes and screw conveyor 42 stops. Subsequently, gate 46 on cement batcher 45 opens to discharge a predetermined amount of cement to chute 47 from whence it is discharged into drum 100 of mixer 11 through its opening 110. Preferably. the aggregate and cement are discharged concurrently into drum 100 of mixer ll, along with necessary water. The electric motors 103 and 104 operate to rotate drum 100 of mixer 11 while it is being filled.

When drum 100 of mixer 11 has received the weighed batches of cement and aggregate and necessary water. the swing chute 47 is swung clear of the mouth of drum 100 of mixer 11 and the threeposition traverse control valves 162 and 163 are oper ated simultaneously (and in synchronism) so as to energize the traverse motors 122 of the mixers 11 and 12, in the appropriate direction to cause rotation of the mixer drive wheels 112 and movement of the mixers 11 and [2 together form one location shown in FIG. 5 wherein mixer ll is aligned with the centerline of plant it] and mixer 12 is at the upper side (with respect to FIG. 5) of plant to another location wherein mixer 12 is aligned with the centerline of the plant and mixer H is at the lower side (with respect to H6. 5) of the plant. PK]. 5 shows mixer 11 in phantom lines as being disposed in the said other location.

When the mixers reach the said other location. the traverse valves [62 and 163 operate simultaneously to stop the traverse drive motors 122 and the tilt valve 165 subsequently operates to energize the tilt cylinders 95 of mixer ll to tilt its drum H0 downwardly and discharge its load into waiting truck 20, for example.

While mixer 11 is discharging its load, mixer 12 is rotating and receiving a charge from plant 10 in the mam ner hereinbefore described. After the drum 100 of mixer 12 is charged and the drum 100 of mixer 11 is discharged, and either after or while the drum of mixer H is restored to upright position, the traverse valves 162 and 163 again operate to energize the traverse motors 122 of the mixers 11 and 12 simultaneously to move the mixers together from the aforesaid other location to the aforesaid one location which was their original location, wherein the drum 100 of mixer 12 tilts and discharges its load while the drum 100 of mixer 11 is refilled. The above-described cycle is repeated as often as necessary.

It will be apparent to those skilled in the art that the present invention may be embodied in apparatus em ploying a batch plant and mixers of a type other than that shown and described herein. Furthermore, the type of drum employed on the mixers may be constructed and operated differently than that disclosed herein. For example, a mixer employing a drum which is tiltable but non-rotatable and having rotary blades therewithin could be employed. Furthermore. the erecting rams, the tilting cylinders, the drum rotation motors, and the traverse motors could take other forms provided they performed the necessary functions. Similarly, the electrohydraulic control circuit could take a form other than that shown and could employ other types of valves.

It would also be apparent to those skilled in the art that the invention disclosed herein facilitates operation and reduces costs in construction work because the batch plant 10 can be operated virtually continuously and each of the two mixers is always in a state of opera tion in that it is either being charged, mixing, discharging, or returning to its charging location. Furthermore. the arrangement disclosed in accordance with the in vention facilitates loading of mix trucks or dump trucks with the cement mix. Thus, while one truck is in a location wherein it is being filled by one mixer, another truck can be moved into a location wherein it will receive mix from the other mixer when the latter moves into such location. Also, if preferred, both mixers H and 12 could be driven by a single traverse motor such as 122 since the mixers are detachably connected to gether.

I claim:

1. In combination: a batch plant for supplying material from a discharge outlet thereon, guide rail means spaced from said discharge outlet, a plurality of mixers mounted for movement on said guide rail means, each of said mixers comprising guide wheels for engagement with said guide rails means. said guide rail means com- 8 prising a pair of spaced apart guide rail assemblies and each guide rail assembly comprising a lower rail engageable with said guide wheels and at least one guide rail assembly comprising an upper rail engageable with S at least some of said guide wheels to prevent said mixers from tipping over, each mixer having a drum thereon for receiving material from said discharge outlet and for discharging said material after it has been mixed, means for detachably connecting said plurality H) of mixers together to enable simultaneous movement of said plurality of mixers on said guide rail means. and means including drive means for moving said plurality of mixers simultaneously on said guide rail means first in one direction and then in another direction so that t5 the drum on one mixer is in a location to receive material from said discharge outlet while the drum of another mixer is in another location to discharge mixed material.

2. A combination according to claim 1 wherein each mixer includes means for moving the drum of each mixer between lowered and raised positions.

3. A combination according to claim 2 wherein each mixer is mobile and comprises ground engaging wheels enabling over-the-road transport.

4. A combination according to claim 3 wherein the drum of each mixer is tiltable between charge and dis charge positions and is rotatable to effect mixing and further including means for selectively tilting and rotating said drums.

30 S. A combination according to claim 3 wherein said batch plant is mobile and comprises ground engaging wheels enabling over-the-road transport.

6. in combination: a batch plant for supplying material from an elevated discharge outlet thereon, guide rail means spaced from and relatively below said dis charge outlet, a plurality of mobile mixers for supplying vehicles. each mixer having ground engaging wheels enabling overthe-road transport and further having guide wheels for engagement with said guide rail means, each mixer having a drum thereon for receiving material from said discharge outlet and for mixing and discharging said material into said other vehicles after it has been mixed, means for detachably connecting said plurality of mixers together to enable simultaneous movement of said plurality of mixers on said guide rail means. and means including reversible drive means for at least one of said guide wheels on one of said mixers for moving said plurality of mixers simultaneously on said guide rail means first in one direction and then in another direction so that the drum of one mixer is in one location to receive material from said discharge outlet while the drum of another mixer is in another location to discharge mixed material into one of said vehicles.

7. A combination according to claim 6 wherein said ground engaging wheels on each mixer are transverse to the guide wheels on each mixer.

8. A combination according to claim 6 wherein each mixer includes means for moving the drum of each mixer between a lowered position for overthe-road transport of the mixer and an elevated position wherein said drum is below said discharge outlet of said plant when said mixer is in said one location and wherein said drum is above one of said vehicles when said mixer is in said other location.

9. A combination according to claim 8 wherein said reversible drive means includes a hydraulic motor and drum of each mixer is tiltuble heiwccn charge and discharge positions and rotatable. and including a hydraulic tilt rum for tilting said drum, said tilt ram being operable by said hydraulic control mcans. 

1. In combination: a batch plant for supplying material from a discharge outlet thereon, guide rail means spaced from said discharge outlet, a plurality of mixers mounted for movement on said guide rail means, each of said mixers comprising guide wheels for engagement with said guide rails means, said guide rail means comprising a pair of spaced apart guide rail assemblies and each guide rail assembly comprising a lower rail engageable with said guide wheels and at least one guide rail assembly comprising an upper rail engageable with at least some of said guide wheels to prevent said mixers from tipping over, each mixer having a drum thereon for receiving material from said discharge outlet and for discharging said material after it has been mixed, means for detachably connecting said plurality of mixers together to enable simultaneous movement of said plurality of mixers on said guide rail means, and means including drive means for moving said plurality of mixers simultaneously on said guide rail means first in one direction and then in another direction so that the drum on one mixer is in a location to receive material from said discharge outlet while the drum of another mixer is in another location to discharge mixed material.
 2. A combination according to claim 1 wherein each mixer includes means for moving the drum of each mixer between lowered and raised positions.
 3. A combination according to claim 2 wherein each mixer is mobile and comprises ground engaging wheels enabling over-the-road transport.
 4. A combination according to claim 3 wherein the drum of each mixer is tiltable between charge and discharge positions and is rotatable to effect mixing and further including means for selectively tilting and rotating said drums.
 5. A combination according to claim 3 wherein said batch plant is mobile and comprises ground engaging wheels enabling over-the-road transport.
 6. In combination: a batch plant for supplying material from an elevated discharge outlet thereon, guide rail means spaced from and relatively below said discharge outlet, a plurality of mobile mixers for supplying vehicles, each mixer having ground engaging wheels enabling over-the-road transport and further having guide wheels for engagement with said guide rail means, each mixer having a drum thereon for receiving material from said discharge outlet and for mixing and discharging said material into said other vehicles after it has been mixed, means for detachably connecting said plurality of mixers together to enable simultaneous movement of said plurality of mixers on said guide rail means, and means including reversible drive means for at least one of said guide wheels on one of said mixers for moving said plurality of mixers simultaneously on said guide rail means first in one direction and then in another direction so that the drum of one mixer is in one location to receive material from said discharge outlet while the drum of another mixer is in another location to discharge mixed material into one of said vehicles.
 7. A combination according to claim 6 wherein said ground engaging wheels on each mixer are transverse to the guide wheels on each mixer.
 8. A combination according to claim 6 wherein each mixer includes means for moving the drum of each mixer between a lowered position for over-the-road transport of the mixer and an elevated position wherein said drum is below said discharge outleT of said plant when said mixer is in said one location and wherein said drum is above one of said vehicles when said mixer is in said other location.
 9. A combination according to claim 8 wherein said reversible drive means includes a hydraulic motor and wherein said means for moving said drum between lowered and elevated positions includes a hydraulic erection ram, and further including hydraulic control means for operating said motor and said erection ram.
 10. A combination according to claim 9 wherein the drum of each mixer is tiltable between charge and discharge positions and rotatable, and including a hydraulic tilt ram for tilting said drum, said tilt ram being operable by said hydraulic control means. 